Figure 7. PEG-conjugated catalase attenuates the beneficial effect of ET receptor antagonism on NO signaling in lambs acutely exposed to increased pulmonary blood flow.

PBF was acutely increased in 4-week old lambs. Lambs were treated with the ET receptor antagonist tezosentan (0.5 mg/kg/hr) in combination with PEG-catalase (15,000 units/kg). Lung biopsies were taken before (Pre) and 4h after (Post), the increase in PBF. In contrast to the findings in tezosentan-treated lambs, lambs treated with tezosentan in combination with PEG-catalase, did not demonstrate increases in lung tissue H₂O₂ levels, as estimated by H₂DCFDA oxidation, after 4h of increased PBF (A). Lysates (40μg) prepared from Pre and Post lung biopsies were subjected to Western blot analysis and probed with anti-pSer1177- or anti-pThr495-eNOS antibodies. For normalization, duplicate samples were run and blotted, then probed with an antibody for total eNOS. In contrast to the findings in tezosentan-treated lambs, lambs treated with tezosentan in combination with PEG-catalase, did not demonstrate increases in pSer1177 eNOS levels after 4h of increased PBF (B) while pThr495 levels were increased (C). Lung tissue NO_X levels did not increase in lambs treated with tezosentan in combination with PEG-catalase (D). Data are mean ± SEM; n =4. *P <0.05 vs. pre shunt opening.